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Question: Answered & Verified by Expert
A heat engine has an efficiency \( \eta \). Temperatures of source and sink are each decreased by \( 100 \mathrm{~K} \). Then, the efficiency of the engine.
PhysicsThermodynamicsJEE Main
Options:
  • A Increases
  • B Decreases
  • C Remains constant
  • D Becomes \( 1 \)
Solution:
1325 Upvotes Verified Answer
The correct answer is: Increases
η = 1 - T 2 T 1 = T 1 - T 2 T 1
where T1 and T2 are the temperatures of a source and sink respectively.
When T1 and T2 both are decreased by 100 K each, (T1 - T2) stays constant. T1 decreases.
∴     η increases.

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